Watermelon and Marijuana at same place.

Neither. As it doesn't really matter mate Once you can tell which seed is which. Idk how many times I've had to re-do seeds and toss viables just cause I mixed them up. True stoner lol. I've no idea what Mel seeds look like. But when you say bags, you do mean just separate right Cannabis seeds need to breathe. So paper-towel or or floating on top of water (if your seeds sink to the bottom by design or themselves, try not leave them as the chances of them drowning increase and lower germ rates. A good germ meth is 24 hrs floating on top of water. (Or until the seed splits and throws out a tiny white tail) then move into a few layers of PT soak really well, (ill explain why) after this is done. Move your seeds to a warm area. Most ppl put on top of their fridge. Once you can hold an air temperature of 20-25c (these are optimal temps but obviously can be done out of these ranges) Tapid water (tap is fine) although if you've a brita filter or bottled water will be optimal for your GOW method, "(more so if you've really hard water) again, these things only make the a small difference, if any Good Growing